**Percent Yield**

What is percent yield? It is the ratio. A ratio of what? It is a ratio of amount of product

**OBTAINED**to the amount of product

**EXPECTED**by calculation. It must be expressed at a %.

Here is an example:

By using this reaction: C3H6Cl2 + 2 KSCN -> C3H6(SCN)2 + 2KCL

The percent yield is 52.0%. How many grams of C3H6(SCN)2 will be produced if 1.5 g of C3H6Cl2 is reacted with excess KSCN?

First, we got to calculate the amount of C3H6(SCN)2 expected to be produced when 120 g of C3H6Cl2 reacts.

1.5 g C3H6Cl2 x

__1 mol C3H6Cl2__x

__1 mol C3H6(SCN)2__x

__158 g C3H6(SCN)2__

113 g C3H6Cl2 1 mol C3H6Cl2 1 mol C3H6(SCN)2

= 2.10 g of C3H6(SCN)2

Now that we have the amount of C3H6(SCN)2 expected, we have the bottom of the fraction, the predicted mass of the product. We know that the end percent yield is 52%, we will have to solve for the top.

% yield =

__C3H6(SCN)2 obtained__x 100% = 52.0 % yeild

2.10 g of C3H6(SCN)2

52.0 x 2.10 = 109.2/100 = 1.09 g of C3H6(SCN)2 obtained.

**Percent Purity**

It is the ratio of the mass of impure substance to the mass of impure substance. The fraction is just like percent yield but on top is mass of pure substance over mass of impure substance all multiplied by 100.

Example:

If a 5.00 g sample of iron ore contains 0.25 g of iron metal, what is the percent purity?

__Mass of pure substance__x 100 = percent purity

Mass of impure substance

__0.25 g Iron__x 100% = 5.00%

5.00 g Iron ore

Percent Yield: